Barley (Hordeum vulgare L.) is the world's fourth most important cereal crop, grown annually on 48 million hectares (Consultative Group on International Agricultural Research 2012), and like other food crops grown as monocultures, uses significant inputs of chemical fertilisers. According to one estimate, application of N-P-K fertilisers to barley crops worldwide will be over 4 million metric tons in 2014, which represents large economic and environmental costs, with ecosystem degradation and potential losses in biodiversity. Ways of reducing these costs whilst still maintaining acceptable yields are required if sustainable agricultural practices are to be widely adopted. Infecting barley with beneficial endophytic organisms may provide part of the solution.
As well as being economically costly, chemical crop treatments for pathogens can have severe and long-lasting negative effects on the environment and reduce biodiversity. While these chemicals can be effective in controlling pathogens in a single cropping season, infections which are transmitted vertically offer more of a challenge. Some seed-borne pathogenic microorganisms may survive seed treatments that are routinely applied. The consequent never-ending cycle of annual fungicidal crop treatments results in large cumulative economic and environmental costs. Alternative control measures using biological organisms may provide a more environmentally-friendly and long lasting solution.
Integrated Pest Management (IPM) methods can be effective in controlling some pathogens and goes some way to reducing chemical use (United Nations 2013). A more promising strategy that uses no chemicals involves exploiting the pathogen control potential offered by endophytes. Endophytes are microorganisms (bacteria, fungi and unicellular eukaryotes) which can live at least part of their life cycle inter- or intracellularly inside of plants usually without inducing pathogenic symptoms. This can include competent, facultative, obligate, opportunistic and passenger endophytes. Endophytes can have several functions and/or may change function during their lifecycle. The fungal root endophyte (Piriformospora indica) has been shown to supress pathogenic fungal development in barley in controlled environment experiments.
In PCT Publication No. WO 2014/121366, endophytes are described as playing a role in plant biomass production and yield in plants such as barley, and also enhances tolerance to environment stresses. In GB 2490249, compositions are described which increased seed vigour and growth. The compositions are used to coat seeds and can comprise endophytes.
Endophytes have also been shown to increase biomass in food crops, and the model endophyte Piriformospora indica increases grain yield (Murphy et al. 2014). Piriformospora indica was first isolated from the roots of desert shrubs in north-west India, and although it has been shown to increase grain yield in cool-cultivated barley under some circumstances, it may not generally be suitable for use in cooler growing conditions.
While there have been studies which examined the interactions between endophyte isolates derived from other plant genera and some important barley pathogens, there is a lack of information on the interactions between endophytes derived from wild barley species and barley cultivars. Several studies have investigated disease resistance genes derived from the wild Hordeum vulgare ssp. spontaneum, for barley diseases such as rust and spot blotch. While these genes represent significant breeding potential for cultivated barley, known diseases will evolve greater virulence as a result
It is the intention of the invention to overcome at least one of the above-referenced problems.